To evaluate the efficacy and safety of the cladribine, busulfan, and cytarabine (CBA) -based intensified conditioning regimen for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with high-risk acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) .

Clinical data of AML/MDS patients who underwent CBA-based allo-HSCT at the Department of Hematology, 940th Hospital of the Joint Logistics Support Force from January 2018 to May 2024 were retrospectively analyzed. Engraftment kinetics, incidence of graft-versus-host disease (GVHD), infections, relapse rates, overall survival (OS), and progression-free survival (PFS) were summarized. Survival rates were analyzed using the Kaplan-Meier method, while cumulative incidence of relapse and non-relapse mortality were evaluated by the Fine-Gray competing risk model. Differences between groups were compared using the Log-rank test.

Twenty-four patients were included, with a median age of 35 (range: 6 ~ 52) years including 15 AML cases (including 13 relapsed/refractory AML) and 9 MDS cases. All patients achieved successful neutrophil with median time to engraftment of 18 (13 ~ 22) days. 22 patients achieved successful platelet engraftment with median time to engraftment of 17 (9 ~ 30) days, and 2 patients of poor platelet engraftment function were relieved after treatment. The incidences of acute and chronic GVHD were 45.8 % and 16.7 %, respectively. All 24 patients achieved complete remission (CR) after transplantation, with the flow cytometry-confirmed MRD was negative. After a median follow-up of 44.5 (1.5 ~ 84) months, the estimated 3-year OS and PFS rates were 57.8% (95%CI: 35.7%~74.6%) and 48.9% (95%CI: 27.8% ~ 67.0%), respectively. The 3-year OS rates of AML and MDS patients were 52.5% (95%CI: 25.2%~ 73.9%) and 66.7% (95%CI: 28.2%~ 87.8%), while PFS rates were 45.0% (95%CI: 19.4%~ 67.8%) and 55.6% (95%CI: 20.4%~ 80.4%), showing no statistically significant difference. The 3-year cumulative relapse rate and non-relapse mortality were 21.6% (95%CI: 7.5% ~ 40.4%) and 29.4% (95%CI: 12.6%~ 48.4%), respectively.

For high-risk AML/MDS patients, receiving the CBA conditioning regimen demonstrates low relapse rates, prolonged overall survival, and favorable safety profiles post-allo-HSCT.